1. Field of the Invention
The present invention relates to image coding and decoding, and more particularly, to an apparatus and method for coding and decoding a digital image with an improved coding efficiency. The digital image includes noise such as a film grain component generated in an image when a movie film is digitized.
2. Description of the Related Art
Conventional coding of an image is performed through processes of performing spatio-temporal prediction, coding a RGB signal of a residue image obtained by subtracting a predicted image from an input image, transforming and quantizing the coded RGB signal, and generating a bit stream with respect to the transformed and quantized image.
In the coding of the image using spatio-temporal prediction, intra spatial predictive coding is used to predict a pixel value of a current block using a spatial correlation of the image. More specifically, the pixel value of the current block is predicted by calculating a difference value between the coded pixel value of an adjacent block and the pixel value of the current block. In inter temporal predictive coding an image is coded by subtracting a current image from a previous image.
Coding efficiency of a general image can be greatly improved by performing the spatial and temporal predictive coding processes with various kinds of methods in ISO/IEC MPEG established for coding of a high quality image and H.264/MPEG-4pt. 10 AVC FRExt standardization technology (“Fidelity range extensions amendment to ITU-T Rec. H.254|ISO/IEC 14496-10,” ISO/IEC JTC1/SC29/WG11 and ITU-TSG16 Q.6, Document JVT-L047 (2004)) of Joint Video Team of ITU-T VCEG.
However, in coding of an image according to the prior art, the noise of the image is removed and then the image is coded to improve coding efficiency. In this case, the noise such as a film grain component is necessary information to give a cinematic effect in the image, and thus, if removed, the cinematic effect disappears.
Accordingly, technology is required to code and decode an image without removing noise such as the film grain component.